Dioptrical chart.



. or the ametrope at any given age.

UNITED STATES Patented March i15, 1904.

VILLIAM VILLARD MARTIN, OF SALEM, RGON.

DIOPTRICAL CHART.

SPECIFICATION forming part of Letters Patent No. 754,663, dated March15, 1904.

Application filed May 4, 1903. Serial No. 155,647. (No model.)

To all 1,071,070@ t nfl/ty concern.

Be it known that I, VILLIAM VVTLLARD MAR- TIN, a citizen of the UnitedStates, residing at Salem, in the county of Marion and State of Oregon,have invented a new and useful Dioptrical Chart, of which the followingis a specification.

The object of this chart is to give the accommodative power present inthe eye at different ages. I/Vith advancing age the accommodationgradually diminishes. This failure of the accommodation begins as earlyas the tenth year and occurs in all eyes, Whatever their refraction.Although all people do not have exactly the same amplitude ofaccommodation at any given age, still there is much less variation thanone would naturally suppose, so little, in fact, that we may safely relyupon this chart in at least ninety per cent. of our cases.

The accompanying drawings are upon a scale of five years, because itwould crowd it to give each year, and one set of lenses is sufficientfor nearly all patients for a period of five years without changing.

The dioptrical chart when put up is neatly framed, like a picture, witha good heavy glass. A hole is drilled through the center of the glass. Abolt passes through the glass, fastening the indexes on the outside infront ofthe chart. The indexes are made of any suitable material thatcan be washed and kept clean.v

The'chart may be made any practical size.

Abbreviations and signs: Cm., centimeter; D., diopters; My., myopia;Hm., hypermetropia; N., minus or negative; o0, infinity; P. P., punctumproximum, (near point;) P. R., punctum remotum, (far point.)

The chart gives the punctum proximum in centimeters and the amplitude ofaccommodation in diopters possessed by the emmetrope To attain this isthe aim of this chart and will be more fully set forth in detail. i

The dioptrical chart is not intended to write prescriptions from,although it would be correct in about ninety per cent. of our cases. Itis intended as an assistant to the optician and will work in harmonywith the retinoscope,

l the ophthalmoscope, or any `other instrument used by the Opticians tomeasure the refraction of the eye, and a great help in estimating hiscases.

In the drawings, Figure 1 represents the plan of the dioptrical chartwith the indexes as they are held in place by the bolt D. indexes areallowed to be turned or moved to different positions on the chart. Erepresents a small handle to be used in moving the indexes. Fig. 2represents the disk A with P. R. (punctum remotum) index B. This indexisdrawn upon or fastened onto the disk and moves with it. Fig. 3represents the twoended index C. One end is marked age and refers to therow of figures marked Age on the chart. The other end of the index C ismarked A. of A. (amplitude of accommodation.) It also refers to allreadings in the same radius. The graduated scale F refers to one-fourthdiopters. The arrow merely shows the top of the chart.

When the retina is situated exactly at the principal focal distance ofthe refracting system of the eye, this condition is called "emmetropiaand is the unit of measure for the optician, as its refraction is thenearest to perfection. It is always the object of the optician to puthis patient, no matter what his refraction, on a footing with theemmetrope. When he has attained this, it is all he can do.

It has been proven that the failure of the accommodation begins as earlyas the tenth year.

Ie will now consider a patient by the chart, knowing him to be anemmetrope ten years of age. The punctum remotum of an emmetrope is atinfinity, which for all practical purposes may be considered as sixmeters, (or beyond.) so we will place P. R. index upon the radius markedco (infinity) and place index marked age upon the ten-year radius. Theupper end of the index gives his punctum proximum seven centimeters andin the same radius, his amplitude of accommodation fourteen diopters. Tomake it clearer, the punctum remotum is the most distant point at whichobjects are seen distinctly. The publication, Refi/action 0 f lt@ Eye,by Gustavus The.

Hartridge, (tenth edition,) P. Blackistons Sons & (lo. 1012 falnutstreet, Philadelphia, page 28, states: lnlinity is any distance beyondsix meters, the rays coming from a point at or beyond that distancebeing parallel or almost so. The emmetropic eye, therefore, has its farpoint, or punctum remotum, situated at infinity. "he hypermetropic eyehas its punctum remotum beyond inlinity, and the myopie eye has itspunctum remotum at a linite distance. At iifteen years of age hispunctum proXimum is at eight centimeters and his amplitude ofaccommodation twelve diopters. At the age of twenty years his punctumproximum is at ten centimeters and his amplitude of accommodation tendiopters. At the age of twenty-five years his punctum proximum is attwelve centimeters, his amplitude of accommodation 8. 50 diopters. Atthe age of thirty years his punctum proXimum is at fourteen centimetersand his amplitude of accommodation seven diopters. At thirtyfive yearsof ag'e his punctum proximum is at eighteen centimeters, his amplitudeof accommodation 5. 50 diopters. At forty years of age his punctumproximum is at twenty-five centimeters, his amplitude of accommodationfour diopters. At forty-five years of ag'e his punctum proximum hasreceded to thirty-three centimeters His amplitude of accommodation isonly three diopters. Thirty-three centimeters equal three diopters, thusshowing our emmetrope is becoming' presbyopic. As he has to use all hisaccommodation to see distinctly at this point, he can do so for anshorttime only without fatigue. Therefore we will have to help him, and theonly way is by giving the proper glasses.

It has been proven that an emmetrope can only use two-thirds tothree-fourths of his amplitude of accommodation without fatigue. Thisbeing the case, our patient can only use continuously about two dioptersof his accommodation or two-thirds of the whole accommodati on, as hewishes to read at thirty-three centimeters, which requires threediopters of accommodation, and as he is only capable of using twodiopters comfortably we must give him ap'air of plus glasses of onediopter to make up the three diopters, thus leaving' him a reserve ofone-third of his amplitude of accommodation. So we look at the age endof index C in the outside row in the same radius and it says give himplus 0.75 to one diopter (sometimes a patient for their lirst glasseswill not accept full correction is why the chart readsplus 0.7 5 to onediopter.) At fifty years of age his punctum proximum is at fiftycentimeters. His amplitude of accommodation is two diopters, two-thirdsof two diopters, 1.25 diopters; his reserve, 0.7 5 diopters. 1.25diopters plus 1.75 diopters equals three diopters. Then hiscorrecting-glasses would be 1.75 diopters to two diopters.

Look in the same radius in the outside row to the right. At the age offifty-live years his punctum proXimum is at sixty-six and twothirdscentimeters and his amplitude of accommodation is 1.50 diopters. At thisage we notice that the punctum remotum is also beginning to recede tothe minus or negative side or beyond inlinity, (here move thepunctum-remotum index on to one point, 0.25 diopters on the scale R)thus showing' our emmetrope is becoming hypermetropic. This is not dueto presbyopia or to the loss of accommodation, for the punctum remotumrepresents the Ladjustment of the eye at rest and is not influenced bythe changes which are weakening its workin g power, but is caused by thecrystalline lens becoming' flattened by ag'e, thereby losing' a part ofits positive refraction. So we see at this ag'e our patient has taken on0.25 diopters of hypermetropia. Look in the outside row to the leftmarked Acquired hypermetropia in the same radius. As his punctum remotumis still on the positive side of in linity, his amplitude ofaccommodation is 1. 50 diopters. Hc can use two-thirds of his amplitudeof accommodation, which is one diopter, to make up thirty-threecentimeters, equals three diopters. TV e will have to give him a pair oflens plus two diopters and to correct his acquired hypermetropia add0.25. Then we have two plus 0.25, 2.25 diopters. These are his correctglasses for reading. At the age of sixty years his punctum proximum hasreceded to one hundred centimeters, with only one diopter ofaccommodation, so he cannot use over 0.50 diopters of his accommodation.Te will have to add 2.50 diopters to make up three diopters, and hisacquired hypermetropia is 0.50 diopter-2.50 plus .50 equals threediopters so we will give him 2.75 to three diopters for his correction.At the age of sixty-live his amplitude of accommodation is from 0.50 to0.75 diopters, and he can use from 0.25 to 0.50 diopters. Then we mustadd 2.50 to 2.75l diopters, plus his acquired hypermetropia, which is0.75 diopters. 2.50plus 0.75, 3.25', to 2.75 plus 0.75 equals 3.50diopters, his correcting glasses. At seventy years of age his punctumproximum is at a negative point. He has 0.50 diopters of accommodation.He may be able to use 0.25 diopters continuously, or he may not, so wewill have to add 2.75 to three diopters. His hypermetropia is now 1.25diopters, so we have 2.75 plus 1.25 equals four diopters, to three plus1.25 equals 4.25 diopters as his correcting-glasses. tive and after hehas no accommodation, so we will have to supply him with the fullstrength for reading. If he wishes to read at thirtythree centimeters,we will give him three diopters plus acquired hypermetropia. 1.50 plusthree equals 1.50 diopters, his readingglasses.4 At eighty years of ag'ehis acquired At the age of seventy- IOO IIO

hypermetropia has reached three diopters, and we have to give him threediopters for his accommodation. Then we have three plus three dioptersequals six diopters, his glasses for reading.

If we wish to consider an ametropic eye, we have only to place the P.It. index on the figuresrepresenting the punctum remotum of the patient.For instance, we are considering a myope of one diopter. We will placeP. R. index on the figures 100 and l D. in the myopic row. His punctumremotum is then at one hundred centimeters or one meter. Place the ageindex at ten years. The A. of A. end of the index shows him to have anamplitude of fourteen diopters, the same as the emmetrope; but by reasonof his defect he has Jfourteen plus one diopter equals fifteen, then onehundred fifteenths six and two-thirds for his punctum proximum. Atfifteen years of age his amplitude is thirteen diopters. At twenty yearsof age his amplitude is eleven diopters, and so on.

Example: Suppose the desired working distance to be thirty-threecentimeters. The amplitude of accommodation is 1.50 diopters and therefraction of the eye one diopter myopia, two-thirds of theaccommodation, one diopter. Subtract from the glass representingthirty-three centimeters three diopters, leaves a remainder of twodiopters. Add this to distance correction minus one diopter added toplus tWo diopters, combined, leaves an optical effect of plus onediopter, which is the glass we prescribe for a patient fifty years ofage.

Pointer B is used only to hold in view the punctum remotum of thepatient under consideration, thus saving recording it or holding it inmemory and leaving it to refer to after the patient has left the office,when a full record can be made in the record-book from the machine orchart.

The scale F is only marked for acquired hypermetropia, simplehypermetropia, and emmetropia. It is not marked off in the myopic row atall, as a myope even of onediopter would not become hypermetropic untileighty years of age.

The pointer B is always placed on the punctum remotum, because as soonas the occulist has determined the punctum remotum of the patient heknows which class the patient be longs to, as the punctum remotum is theindex of the class. AThe punctum remotum of the emmetrope is atinfinity. The hypermetropic eye has its punctum remotum beyond innity.The myopie eye has its punctum remotum at a finite distance.

To consider' a hypermetropic eye, we test the patient by some of theways we havethe trial case, the opthalmoscope, retinoscope, Sac. Say wefind him hypermetropic one di opter. Then we know his punctum remotum isone diopter behind his eye. So to keep our finding weturnBpointer onto lD in thehypermetropic row in the sector inside circle with the word ageEach sector represents a diopter in width. Scale F divides it intoquarters. If the patient Was fifty-five years old, we would set pointerB on the first quarter, thus showing him to have 0.25 of acquiredhypermetropia; but this patient is ten years of age, so we place pointerB age end up on the ten years in age row. The A. of A. end shows ourpatients near point seven centimeters, his amplitude of accommodationfourteen diopters. This would be the same as an emmetrope.

To find the amplitude of accommodation of a hypermetrope, we must add onto the lens whose focal length equals the distance of the near pointthat convex lens which enables him to see distant objects distinctly.Thus our chart will measure the ametrope as well as the emmetrope.

What I do claim as my invention, and desire to secure by Letters Patent,is

The herein-described dioptrical chart, containing formulae indicative ofthe punctum proximum and the amplitude of accommodation of the emmetropeand the ametrope at any given ag'e, in combination with a rotatablesingle index-bearing disk, and a double-ended index rotatableindependently of the single index, both indexes being employed inreading the chart, substantially as described.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

WILLIAM WILIiAItD MARTIN.

Witnesses:

THos. H. RnYNoLDs, J. CLEM LEWIS.

